Rizza's special gift

I told Rizza I was going to bring her a special gift when I go to the Philippines in a few weeks. I mentioned to her I would give her one clue a day as to what it was. Its been rather interesting to come up with the clues and see how she'd speculate as to what it was. She finally figured it out after a week's worth of clues. She cried tears of joy when she realized it was an engagement ring. It was definitely a happy day for her. The last couple of clues are probably what gave it away:

"It has an inside, and outside, but no sides"
"When part of it is put in water, you cannot see it"